WASHINGTON—Republican members of Congress reacted to President
Donald Trump
’s meeting with North Korea’s leader
Kim Jong Un
with cautious optimism, saying they supported the goals outlined in the two-page joint communiqué the two signed after the summit but that it lacked detail and was only a starting point for negotiations.

Democrats focused on the lack of detail in the two-page statement, which reasserted North Korea’s commitment to denuclearization in exchange for unspecified U.S. security assurances, saying the summit had legitimized a brutal regime and failed to make progress on the nuclear issue. They also criticized Mr. Trump’s decision to unilaterally suspend military exercises with South Korea without consulting with Seoul.

“Only time will tell if North Korea is serious this time, and in the meantime we must continue to apply maximum economic pressure,” said House Speaker
Paul Ryan
(R., Wis.), referring to the sanctions framework the U.S. and its allies have imposed on North Korea, a pariah for decades.

Sen.
Bob Corker
of Tennessee, the Republican chairman of the Senate Foreign Relations Committee, was also circumspect, saying: “While I am glad the president and Kim Jong Un were able to meet, it is difficult to determine what of concrete nature has occurred.”

“I don’t think canceling a war game is going to matter over the arc of time,” Sen.
Lindsey Graham
of South Carolina, a senior Republican on the Senate Armed Services Committee, told NBC. “The one thing that I would violently disagree with is removing our troops.”

Sen. Graham noted that two previous Korean peace summits—in 2000 and 2007—failed to end nuclear-weapons testing or secure lasting stability on the peninsula.

Sen.
Tom Cotton
(R., Ark.) said in a radio interview he believed the “proof of the pudding will be in the eating,” noting the next large-scale joint military exercise wasn’t scheduled until spring of 2019.

“I suspect by that point, we’ll have, well before that point, actually, we’ll know whether Kim Jong Un is serious about these commitments,” he said. “I believe that Donald Trump is going to continue the campaign of maximum pressure, and he will not grant one-sided unilateral concessions.”

“The president handed Kim Jong Un concessions in exchange for vague promises that do not approach a clear and comprehensive pathway to denuclearization and nonproliferation,” she said.

Senate Minority Leader
Chuck Schumer
(D., N.Y.) and other Democrats expressed doubt that the meeting would lead to any concrete results.

“What the United States has gained is vague and unverifiable at best. What North Korea has gained, however, is tangible and lasting,” Mr. Schumer said on the Senate floor. “President Trump has granted a brutal and repressive dictatorship the international legitimacy it has long craved.”

Sen.
Brian Schatz
of Hawaii, which is believed to be within range of North Korea’s missiles, said the president’s positive comments about the North Korean leader reflected an “abdication of American leadership,” calling the remarks “embarrassing.”

“What did we get? Do we get something later? Because it looks like [Mr. Kim] got all the stuff. Does our stuff get announced in a few months?” Sen. Schatz, a Democrat, wrote on Twitter shortly after the summit concluded.

Former National Security Agency and Central Intelligence Agency director
Michael Hayden
said the U.S. had made a “pretty significant concession” in agreeing to halt joint military exercises with South Korea. He said a scorecard at this stage would show the North Koreans “way ahead on points” for having been treated as equals in negotiations on the world stage.

Joseph DeTrani,
a former CIA official who served as a U.S. special envoy to the six-party talks that fell apart after North Korea conducted a ballistic missile test in 2009, said the meeting was a welcome first step.

“I know I am probably an outlier on this, but just holding the meeting is a success,” Mr. DeTrani told The Wall Street Journal, adding that Mr. Kim’s moratorium on missile launches was also a good sign. “You don’t come this far unless you really have something in hand.”

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Joseph Yun, a U.S. special representative for North Korea policy during the Obama and Trump administrations who announced his retirement in February, said the outcome of the summit had been disappointing.

“It’s not at all clear what the next steps are,” Mr. Yun said. “He (Mr. Trump) gave in on what denuclearization is and how long it will take, he kicked that can down the road.”

He said the lack of detail in the joint statement could make it more difficult for Mr. Pompeo and his team to extract future concessions from North Korea.

Victor Cha, who helped oversee North Korea policy in President George W. Bush’s second term and is now a Georgetown University professor, said the meeting was just a first step on a long road ahead, and previous negotiations had gone further.

“This is the bare bones of an agreement on denuclearization. On paper the commitment is less than we have got before in 2005 and 1994, though this time it comes from the leader directly,” Mr. Cha told The Wall Street Journal. “Success will be determined by Pompeo’s ability to put some meat on the bones. Otherwise it’s just a photo op.”